CCBC-160 Fix incorrect reschedule of batched commands

* do not call lcb_server_event_handler() directly, but rather schedule it
* properly breakout the while loop in do_read_data()
* do not call recvv() when we are parsing input on WRITE event

Change-Id: Id11fd9d4b15b74aeb1c237f51ed55287685b386d
Reviewed-on: http://review.couchbase.org/23684
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>